feat: Move COSE timestamp generation into c2pa_crypto

[scouten-adobe]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 13.51351% with 64 lines in your changes missing coverage. Please review.

Project coverage is 80.04%. Comparing base (66b57b5) to head (aaf3677).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/crypto/src/cose/sigtst.rs	0.00%	37 Missing ⚠️
internal/crypto/src/time_stamp/provider.rs	0.00%	22 Missing ⚠️
sdk/src/signer.rs	66.66%	3 Missing ⚠️
sdk/src/cose_sign.rs	80.00%	1 Missing ⚠️
sdk/src/error.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #803      +/-   ##
==========================================
- Coverage   80.83%   80.04%   -0.80%     
==========================================
  Files         118      117       -1     
  Lines       30951    30953       +2     
==========================================
- Hits        25019    24775     -244     
- Misses       5932     6178     +246     

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